When using manipulators, such as industrial robots, for machining workpieces, it is also possible to use tools which are able to perform characteristic movements with a number of degrees of freedom in principle independently of a movement of the manipulator. This e.g. applies to industrial robots, which carry at the distal end of the robot arm a laser and controllable focussing optics for the laser machining of workpieces. In this case, the aforementioned tool can e.g. be a laser cutting tool, a laser welding tool or a laser stamping tool, which is equipped with mobile mirror arrangements so as in this way to permit an active working movement of the laser beam, which is equivalent to the aforementioned characteristic movement of the tool.
The mobile mirror arrangements of such laser cutting tools are also known as scanner units or galvano units.
It is known in connection with methods or devices of the aforementioned types to use manipulators for the rough positioning of the tool in the vicinity of a workpiece to be machined and subsequently the tool (in the indicated example the mirror and as a result the laser beam) can follow or track small scale contours of a predetermined machining path. For machining larger scale contours the machining process must be interrupted and the manipulator repositioned. Subsequently the tool located on the manipulator again takes over the small scale machining of the workpiece. Such a procedure involves a time-consuming stop and go process, in which periodically the manipulator is stopped and periodically the tool is stopped. This also leads to unnecessarily large reorientations of the (relatively) slow manipulator.
The known methods and devices for machining workpieces also have further disadvantages. Thus, as a rule it is not possible to achieve a constant machining speed on random machining geometries, because movements of the manipulator, as a result of its greater weight and inertia, always take place with a lower speed than the small scale movements of the tool, particularly in the case of curves and bends in the contours. However, in laser methods a constant machining speed is a basic prerequisite for high quality machining.
Due to the fact that the prior art manipulator and tool are guided independently of one another from the control standpoint, the teaching process preceding machining is not easy to handle and is therefore susceptible to faults and errors, because for this purpose it is necessary to reprogram two controls. In addition, such known methods and devices cannot be given online or real time characteristics, because no paths can be modified at random without the in each case other control also having to be reprogrammed. For the same reason offline programming is only possible to a limited extent.
Other known methods and devices are restricted to the phasewise taking into account of a uniform linear movement of the manipulator, e.g. a conveyor belt or portal welder and are superimposed on the characteristic movements of the tool. Such methods and devices reach their limits when machining complex, randomly shaped surfaces and contours.
Whilst avoiding the aforementioned disadvantages, the problem of the invention is to improve a method and a device of the aforementioned type with regards to an optimum movement of the manipulator and the tool when machining randomly shaped workpieces and the further development of a device of the aforementioned type to be brought about is also to be characterized by real time adaptability and simplified handling, particularly when setting up machining processes.